In one type of offshore well production, a subsea production tree is installed at the sea floor. The tree may be connected by a flowline jumper to a subsea manifold, which is connected to other subsea trees in the vicinity. A production riser may extend from the subsea manifold or from an individual tree to a processing facility, normally a floating platform. The well formation pressure is normally sufficient to cause the well fluid to flow up the well to the tree, and from the tree to the processing facility.
In very deep water, the well may have sufficient pressure to cause the well fluid to flow to the tree but not enough to flow from the sea floor to the processing facility. In other cases, the well may even lack sufficient pressure to flow well fluid to the sea floor. Downhole electrical submersible pumps have been used for many years in surface wells, but because of periodic required maintenance, are not normally employed downhole in a subsea well. A variety of proposals have been made for booster pumps to be installed at the sea floor to boost the well fluid pressure. However, because of the pump size, installation expense and technical difficulties, such installations are rare.